At present, most of the wave power conversion devices in China are in the stage of primary sea trials, and the operation effect of the devices in real sea conditions is generally poor. In order to improve the adaptability of the wave power conversion device and the energy capturing efficiency of the float under small waves, a rocker type wave power conversion device is designed based on the hydraulic transmission system. The device adopts the core technology of wave rack + group cylinder, which overcomes the defect that currently float is connected to only one hydraulic cylinder, resulting in insufficient energy capturing. In order to verify the feasibility of the device, the hydraulic system of the device was simulated by AMESim simulation software based on the design principle; then the device was subject to model test in a hydrodynamic pool. The simulation results show that the hydraulic system of the device can work normally under small waves; the model test results show that the device can generate power continuously and stably even under small waves, and has high energy capturing efficiency of the float in the same type of device; simulation and model test results verify the feasibility of the device design. The study can provide reference for research and design of other wave power conversion devices.